Angel Island, San Francisco Bay, is one of the most geologically interesting places, with pilllow basalts, blueschists and serpentinites and wackes. These rocks have been scraped from the subducting plate and represent remnants of a Jurassic oceanic crust, now completely tectonically mixed, in what is called mélange (mixture in French). The Franciscan mélange was formedContinuar lendo “PILLOW LAVAS, BLUESCHISTS AND OTHER ANCIENT OCEANIC ROCKS / LAVAS EM ALMOFADA, XISTOS AZUIS E OUTRAS ROCHAS OCEÂNICAS ANTIGAS”
Arquivos da categoria: Mountain Belts
THE AGE OF MOUNTAINS AND CONTINENTS FROM TINY MINERALS /A IDADE DAS MONTANHAS E DOS CONTINENTES EM PEQUENOS MINERAIS
Some minerals found in rocks are special in that they accommodate a lot of specific chemical elements in their structures and almost none of other elements. This is the case of zircon (ZrSiO4), which likes Uranium but allow almost no Lead in it’s structure. This turns zircon in an ideal mineral to calculate the ageContinuar lendo “THE AGE OF MOUNTAINS AND CONTINENTS FROM TINY MINERALS /A IDADE DAS MONTANHAS E DOS CONTINENTES EM PEQUENOS MINERAIS”
APATITE FISSION TRACKS and mountain denudation / TRAÇOS DE FISSÃO EM APATITA e denudação das montanhas
Those small minerals can help to understand how quickly a mountain belt is eroded. The method is based on the decay of radiogenic elements within the mineral structure, which leaves small tracks due to the damage caused by the nuclear disintegration. By counting the density and length of the tracks, we can estimate the timeContinuar lendo “APATITE FISSION TRACKS and mountain denudation / TRAÇOS DE FISSÃO EM APATITA e denudação das montanhas”
Project MOBILE 